Drug metabolism is an important process in the body involved in drug elimination as well as in activation of some compounds and the consequential development of toxicities. This project is designed to investigate the potential use of Flubiprofen as a selective probe of CYP2C9 and the possibility of incorporating it into an already developed five drug cocktail. The objective is to be able to use it in large population studies to assess the role of CYP2C9 in the pathogenesis or prognosis of diseases.